In current wireless network scenarios, a device will typically communicate with a network infrastructure node such as a base station or an access point that the device is being served by, which will then allow communication to other devices served by that same network infrastructure node, or to devices served by other network infrastructure nodes. However, such communication may not be possible in remote areas where wireless network coverage from an infrastructure node does not exist. Further, even where wireless network coverage exists, communications using a network infrastructure node may not be desirable. For example, in general communication systems, a direct D2D transmission of data may provide more efficient space division multiplexing than current networks.
Device-to-device communications are communications between two wireless devices or user equipments (UEs), where the communication proceeds directly between UEs and does not proceed through a network infrastructure node. Uses for D2D communications may be for both emergency and non-emergency situations. For example, first responders and public safety members may use D2D communications to communicate between devices. This may be useful in situations where there is no network coverage, such as remote areas or inside a building. However, even in network coverage areas, in some cases D2D communications are desirable in public safety situations.
In non-emergency situations, friends that are in close proximity to each other may wish to communicate with each other. Other cases include devices such as parking meters talking to mobile wireless devices within range to help a mobile wireless device find a free parking space. Other examples are possible.
The operation of a device without a network infrastructure element however has challenges. These include: identifying what devices the UE can communicate with; when receiving, which devices can the UE expect interference from; when transmitting, which devices can the UE expect to interfere; how can a UE signal other devices; what is the timing that the UE uses to communicate with other devices; which resources can be used by individual D2D transmissions so that the receivers face and the transmitters cause low interference; among other challenges.